1. Technical Field
The present disclosure relates to a semiconductor integrated circuit and, more particularly, to a circuit that detects and cuts off an irregular voltage by using a bandgap reference voltage generation circuit.
2. Discussion of Related Art
When an irregular voltage, such as a too high voltage or a too low voltage, is applied to a system in which the range of operating power supply is set, the system cannot operate normally. Specifically, a high voltage can damage the system, and thus a circuit that cuts off a high voltage is required in order to protect the system.
FIG. 1 is a diagram illustrating a conventional protection circuit that can protect a display device from an unstable power supply. Referring to FIG. 1, when an input power-supply voltage Vin is outside a normal operation range, the protection circuit generates a main power-supply on/off signal MS, which forcibly turns off a main switch connecting the input power supply Vin and a power-supply generator (not shown). A reference voltage circuit 130 generates a minimum reference voltage and a maximum reference voltage based on the input power supply voltage Vin by using a sixth resistor R6 and a seventh resistor R7. The maximum reference voltage is inputted to a non-inverting input terminal (+) of a first comparator 122 and the minimum reference voltage is inputted to an inverting input terminal (−) of a second comparator 124.
The first comparator 122 generates a main power-supply control signal PCS by comparing a second voltage of a second node n2, which is stabilized by using a second zener diode ZD2 in a stabilization circuit 120, and the maximum reference voltage. In this example, when the second voltage is lower than the maximum reference voltage, the generated main power-supply control signal PCS is in a high state. The second comparator 124 generates the main power-supply control signal PCS by comparing a first voltage of a first node n1, which is stabilized by using a first zener diode ZD1 in a stabilization circuit 126, and the minimum reference voltage. In this example, when the first voltage is higher than the minimum reference voltage, the generated main power supply control signal PCS is in a high state. The main power-supply control signal PCS is transmitted to an output node nO, and then is stabilized by using a third zener diode ZD3 inside a stabilization circuit 132. Accordingly, the main power-supply control signal PCS is generated as the main power on/off signal MS. Consequently, the main power-supply on/off signal MS is generated in a high level which turns on the main switch in the range between the minimum reference voltage and the maximum reference voltage.
Turn-on voltages of the first, second and the third zener diodes ZD1, ZD2, and ZD3 used in the protection circuit, however, may change according to a process or temperature variations. This enlarges the range between a minimum reference voltage VLon and a maximum reference voltage VHoff controlled by the main power-supply on/off signal MS, such as VLon1 to VHoff1 or VLon2 to VHoff2, as illustrated in FIG. 2.
Accordingly, an irregular voltage detection and cutoff circuit, which can accurately control a voltage range between a minimum reference voltage and a maximum reference voltage, is required.